The cone penetration tests have been employed extensively in both onshore and offshore site investigations to obtain the strength properties of soils. Interpretation of effective internal friction angle gyp' becomes complicated for cones in silty clays or clayey silts, since the soil around the advancing cone may be under partially drained conditions. Although there exist several robust methods to estimate gyp ' , the pore pressure at the cone shoulder has to be measured to represent the drainage conditions. Many cone penetrometers in practice are not equipped with a pore pressure transducer. Even for a piezocone, the pore pressure recorded in-situ may be unreliable due to the poorly saturated or clogged filter. These limitations prohibit the application of existing methods. Large deformation finite element analyses were carried out within the formula of effective stress to reproduce the cone penetrations under various drainage conditions. The numerical approach was validated against the existing model tests in centrifuge and chamber, with wide ranges of penetration rates and soil types. A backbone curve is proposed to estimate the normalized cone resistance varying with the normalized penetration rate. Based on the backbone curve, a procedure is developed to predict gyp' of cohesive soils under undrained or partially drained conditions, replacing the pore pressure with the normalized penetration rate. The procedure can be used for soils with an overconsolidation ratio no larger than 5.

Spherical glass beads weaken the influences of particle morphology, surface properties, and microscopic fabric on shear strength, which is significant for revealing the relationship between macroscopic particle friction mechanisms and the particle size distribution of sand. This paper explores the shear mechanical properties of glass beads with different particle size ratios under different confining pressures. It obtains the particle size ratio and fractal dimension D through an optimal mechanical response. Simultaneously, we explore the range of the fractal dimension D under well-graded conditions. The test results show that the strain-softening degree of R-s is more obvious under a highly effective confining pressure, and the strain-softening degree of R-s can reach 0.669 when the average particle size (d) over bar is 0.5 mm. The changes in the normalized modulus ratio E-u/E-u50 indicate that the particle ratio and arrangement are the fundamental reasons for the different macroscopic shear behaviors of particles. The range of the peak effective internal friction angle phi is 23 degrees similar to 35 degrees, and it first increases and then decreases with the increase in the effective confining pressure. As the average particle size increases, the peak stress ratio M-FL and the peak effective internal friction angle phi first increase and then decrease, and both can be expressed using the Gaussian function. The range of the fractal dimension D for well-graded particles is 1.873 to 2.612, and the corresponding average particle size (d) over bar ranges from 0.433 to 0.598. Under the optimal mechanical properties of glass beads, the particle size ratio of 0.25 mm to 0.75 mm is 23:27, and the fractal dimension D is 2.368. The study results provide a reference for exploring friction mechanics mechanisms and the optimal particle size distributions of isotropic sand.